Essay: Why Did We Drop the Bomb?

The ceremonies marking the 40th anniversary of Hiroshima's obliteration are over, and the ghostly figures of vaporized corpses that were stenciled on the sidewalks of scores of American cities have already begun to fade. What remains is a question, the same one that has gnawed at us from the first: Did the U.S. really have to drop the atomic bomb?

Harry Truman, the man who gave the order, explained often and emphatically that he did so for the simplest yet most compelling of reasons: to end the war. Such surety seems comforting. Yet one thing last week's observances showed is that...